The purpose of this study is to evaluate whether a special external camera called a SPECT camera can detect changes in the blood flow in certain regions of the brain during the distension of the rectum with a balloon. Our data suggest that SPECT identifies regions of cerebral activation during rectal distention in humans; thus, SPECT shows promise for studying cerebral activation during visceral stimulation. We plan to pursue this line of research, incorporating the SPECT technique to investigate patients with GI disease states in order to compare their cerebral activation with our data set of healthy volunteers.